Tuesday, December 16, 2014

Reflections on the Boxing Day Tsunami

To say that the Boxing Day Tsunami had a huge impact is an
understatement. It affected the world, the science community and me. My science
training had not prepared me for the sheer devastation the earthquake and
tsunami did across 19 countries. New Zealand was not immune to the devastation
either; we lost seven kiwis that day. The total loss of life and damage is
beyond comprehension. Today I reflect on the lessons we have learned as a
science community to help ensure the loss of life and damage does not occur on
that massive scale again.

What we couldn’t appreciate at the time was the Boxing Day
tsunami was the start of a decade of deadly and destructive tsunami. These include the
2007 Solomon Islands (Gizo), 2009 Samoan Islands, 2010 Chilean, 2013 Solomon
Islands (Temotu) Tsunami and, the largest of all in the Pacific, the 2011 Japan
tsunami. All these events demonstrated the massive power of the
mega-earthquakes which hugely displace the sea floor and sea water above
causing tsunami.

So what have we learned in this decade of tsunami? Globally,
we learned that we needed a much better tsunami warning capability. Before the 2004
Boxing Day tsunami, the Pacific Tsunami Warning and Mitigation System (PTWS)
was the only tsunami warning system on the planet, but it is now one of four
globally covering the world’s oceans. So at least we have learned that lesson.

In New Zealand, we have changed our tsunami warning system
considerably. We now use tsunami forecast models to establish the potential
threat in pre-defined coastal zones and issue this information in map and text
formats. The threat levels can be used to inform evacuation decisions based on
planned evacuation zones and routes. GNS Science act as the science advisors to
the Ministry of Civil Defense and Emergency Management (MCDEM) employing
forecast models and the expert knowledge of the “Tsunami Experts Panel”, a
group of New Zealand based tsunami scientists.

We also updated the science and technology in the wider Pacific; on 1
October this year PTWS improved its tsunami warning capability using similar
techniques to those we currently employ in New Zealand. Now the Pacific Tsunami
Warning Centre in Hawaii (the operational centre of PTWS) sends pictorial and text messages to member countries based on tsunami forecast models and the
expected impacts on coastlines. This replaces the messaging based solely of the
size and location of possible tsunami-generating earthquakes.

We have done a lot of work in the last decade. But here is
what keeps me awake at night: we still rely totally on natural warnings
(feeling high levels of, or long lasting shaking, and unusual sea behaviour) for
local-source tsunami warning. These are the tsunami caused by earthquakes or triggered
undersea landslides near our coast. And
there are some situations in New Zealand where a tsunami-causing earthquake may
not be felt strongly, leaving a potential gap in our tsunami warning strategy. On
the east coast of the North Island we have a huge fault (the subduction zone)
where the Pacific tectonic plate meets and is pushed down below the Australian
plate. This is similar to the tectonic situation off the coast of Japan. Many
earthquake types can happen in this process, including “slow” earthquake which
will not be strongly felt. And further north of New Zealand, a very large
earthquake could send a tsunami towards cities and townships of the upper North
Island without high levels of shaking being felt on-land (see 2013 GNS Science tsunami hazard update). Two “slow”earthquakes in 1947 caused tsunami which deposited seaweed in power line and damaged
buildings, but thankfully caused no loss of life, in small communities north of
Gisborne.

Work continues on the science and technology necessary to provide
official warnings for these local events for New Zealand, which may provide minutes to 10s of
minutes of warning. Watch this space!

I realise this sounds very “doomsday” scenario. And we
haven’t been affected by a tsunami like this for a long time. But I’d like to
see a local-source tsunami warning capability piloted here in New Zealand. I’m
a realist and know the amount of resources required to make this happen. But the Boxing Day tsunami taught me that the
seemingly impossible can happen. We are more ready than we were in 2004. But we need to be even more ready than we currently are.

The most fundamental lesson we’ve learned though isn’t about
science. It’s that people’s direct actions matter. The day may come when we
have all the scientific systems set up, but we will always need to rely on
ourselves and each other. If you feel a long or strong earthquake on the coast,
evacuate immediately. Here is the best advice about evacuating during a tsunami
(from the MCDEM):

·Take your getaway kit with you if possible. Do not travel into the areas
at risk to get your kit or belongings.

·Take your pets with you if you can do so safely.

·Move immediately to the nearest higher ground, or as far inland as you
can. If evacuation maps are present, follow the routes shown.

·Walk or bike if possible and drive only if essential. If driving, keep
going once you are well outside the evacuation zone to allow room for others
behind you.

·If you cannot escape the tsunami, go to an upper storey of a sturdy
building or climb onto a roof or up a tree, or grab a floating object and hang
on until help arrives.

·Boats are usually safer in water deeper than 20 metres than if they are
on the shore. Move boats out to sea only if there is time and it is safe to do
so.

·Never go to the shore to watch for a tsunami. Stay away
from at-risk areas until the official all-clear is given.

·Listen to your local radio stations as emergency management officials
will be broadcasting the most appropriate advice for your community and
situation.

About Me

I have been the Director of New Zealand GeoNet at GNS Science since 2005. GeoNet is New Zealand’s integrated geological hazards monitor system employing state of the art equipment and telecommunications technology. I am the immediate past chair of the governance group for the Pacific Tsunami Warning and Mitigation System (ICG/PTWS), and a current working group chair.. I am a scientific project manager, seismologist, scientific instrumentation and telecommunications specialist with more than 30 years’ experience. My research has concentrated on geophysical instrumentation, the field studies of large earthquakes, and the study of the deep structure beneath New Zealand and internationally using the seismic waves generated by earthquakes.